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Re: [www-vrml] Why you _can_ convert VRML97 to X3D
(I'm not getting all the emails for this thread. Only
commenting on what is written below)
Any (automatic) conversion of a script node that
relies on dynamic generation of content in classic
VRML encoding is non trivial.
If this type of script behavior is only 1% of all
content I don't know. Personally I don't think anyone
does.
Scripts that load content (VRML) need to provide the
conversion themselves for full portability.
The additional existence of the PROFILE statement and
the fact that is being checked at parsing time also
doesn't help. Assuming that the browsers do enforce
it. Some popular ones don't.
Checking at parsing time also allows for silly
examples
like this
#X3D V3.0 utf8
PROFILE Full
Shape { }
It would be more useful to enforce it after parsing.
(AFAICT the spec doesn't make any requirement on when
the enforcement (if any) should be made.)
>From the spec and section 7.2.5.3 it is unclear that
that the browser needs to respect it at all:
"...and providing a mechanism for strict conformance
should the browser choose to enforce it..." but then
it says
"it may proceed with presenting the world; otherwise,
it shall fail."
BTW there are examples in the spec that do not use the
PROFILE statement at all and others that define it
like this PROFILE "Full". Which one is it?
There is the question of portability that Paul
mentioned. That is a most serious one.
If I have a company with *lots* of VRML content I
won't pay to convert it. Why should I? The whole
premise of ISO is backwards compatibility. If the new
stuff doesn't support it I'll use the old stuff for
it.
What is the purpose of X3D-Edit's warnings? If it is
to enable a author to go and alter the content by hand
then its pointless. Decent 3D content needs to be
built in a DCC tool or with a suite of tools.
The whole VRML build-by-hand world is dead.
Besides, command-line tools are not good enough.
Maybe I'll start a simple converter of my own.
Cheers,
Goncalo
--- Paul Aslin <fabricatorgeneral@yahoo.com> wrote:
>
> One small fly in the ointment. There is no SFNode
> used in
> standard X3D nodes.
>
> ie: X3D Shape has a geometry node but unlike VRML it
> is
> MFNode. Which means it may contain multiple nodes,
> if I am
> reading it right.
>
> So what would happen if SFNode is used in a proto
> and that
> is mapped to a node that uses MFNode. More seriously
> wouldn't this require changes to Script nodes which
> also
> access the same field.
>
>
> As for comments about 99% of Scripts working,
> perhaps you
> are right, but I cannot check as SFNode/MFNode usage
> in
> Scripts doesn't seem to work at all in flux at the
> moment.
>
> As a result 99% of my interesting code doesn't work
> at all
> (which includes the one item I need to get working
> in X3d).
>
>
> I'll try out Xj3d and see what results I get with
> that.
>
>
> --- Don Brutzman <brutzman@nps.edu> wrote:
>
> > I think X3D Classic VRML is very close to VRML 97
> and
> > that
> > conversion is easy. And so, couldn't disagree
> more with
> > the original subject line.
> >
> > We've included Qiming Wang's NIST translator in
> X3D-Edit
> > and so
> > it is pretty simple from that environment. There
> are
> > also command-line
> > launchers of the translator included. If
> sufficient
> > interest exists
> > to provide help in further tuning this tool, we
> could put
> > it under cvs.
> >
> >
>
http://www.web3d.org/x3d/content/examples/help.html#Conversions
> >
> > I'd estimate that 99% of all VRML97-embedded
> Javascript
> > will work
> > if the first line of the script, namely
> > javascript:
> > is changed to
> > ecmascript:
> >
> > The ones that still don't work won't have worked
> > consistently beforehand,
> > i.e. they were buggy anyway.
> >
> > A further significant assist is that X3D-Edit's
> > X3dToVrml97 translator
> > provides extensive debugging errors, warnings,
> hints and
> > info messages.
> >
> > An untaken project that might interest someone is
> to make
> > - VrmlToX3d
> > - X3dToVrml
> > - translation debug messages
> > available via server for direct use via web page.
> >
> > all the best, Don
> > --
> > Don Brutzman Naval Postgraduate School, Code
> USW/Br
> > work +1.831.656.2149
> > MOVES Institute, Monterey CA
> 93943-5000
> > USA fax +1.831.656.7599
> > Virtual worlds/underwater robots/X3D/XMSF
> > http://web.nps.navy.mil/~brutzman
> >
>
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